[aerohead]

Laid awake thinking about his San Diego to Florida trek.
Some thoughts:
* 50-mph minimizes the magnitude of heat flux the cooling system must handle. It's conceivable that the lower radiator shutters never opened, minimizing main body drag.
* 50- mph also minimizes 'windage' ( ventilation drag of rotating wheels ).
* 50-mpg minimizes rolling resistance, as it varies arithmetically with speed.
* At 50-mph, any crosswind or gust effects would be minimized.
* At an 'average' 50-mph, ascending grades might be undertaken at 45-mph ( the legal minimum ), minimizing climbing losses ( an old trick of the Mobil Economy Run ). [ An inclinometer in the cabin would inform how speed was chosen ].
* At 81.1% regenerative kinetic energy recovery, one might allow a gravity-assist 'overspeed' on downhills,, which not only increases wheel power for harvesting, it also 'boosts' hill-climbing on the next grade.
* Choosing 'mild' temperatures allows AC 'OFF', windows-up driving, saving on accessory losses.
* Curve resistance is less at 50-mph.
* Vehicles overtaking the 'slow' vehicle may impart a degree of thrust as they pass.
* Tires inflated to maximum sidewall rating?
* Choosing a more conservative acceleration rate than the EPA's Mobile Testing is constrained to use would reduce power demand for all accelerations.
* Opportunity drafting might avail itself ( some trucking companies use telemetered speed governing which the driver cannot defeat ) [ As long as your 'average' speed is 50-mph, you can claim it.
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Hybrid assist and regen makes it near-impossible to parse out what's going on in a hybrid. Emission Analytics testing indicates that 'hybrid' adds 48% to mpg. 80-mpg would become 54-mpg without it.